Illumination – Plural light sources – Particular wavelength
Reexamination Certificate
1999-11-23
2002-11-12
O'Shea, Sandra (Department: 2875)
Illumination
Plural light sources
Particular wavelength
C362S232000, C362S259000, C362S800000, C257S089000, C257S099000
Reexamination Certificate
active
06478447
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to the improvement of a light-emitting diode (LED) light source and, more particularly, to the development of lighting units that homogeneously mix the light beams from LEDs of different shapes to achieve a superior light mixing effect.
2. Related Art
Light-emitting diode (LED) technology has had a great progress. The lighting efficiency and unit luminosity are grown logarithmically. Therefore, using LEDs as lighting units in practice should be within a number of years. However, since each kind of LEDs is made by a different material, the lighting method is also different. This in turn affects the beam shape from the LED. This feature causes no problem in most applications, yet has a great influence on certain situations.
Our company discovers this light source phenomenon when doing research on a special luminaire composed of highly luminous RGB LEDs. So the present invention is accomplished after many times of experiments.
Since the lighting method of LEDs belongs to semiconductor lighting, the light emitted has a unique wavelength. Although there are white LEDs, they are made by having blue light as the primary light and applying a fluorescent to convert the blue light into lights of different wavelengths. Thus the lighting efficiency is not high enough. Under the current circumstances that the LED lighting efficiency cannot be promoted, the RGB LEDs as the light sources have the most efficient luminosity. For example, the luminosity of a single white diode is about 2.0 CD (at the angle of 15 degrees), that of a blue diode is about 3 CD, but that of a green diode can reach 8 CD and that of a red diode can have 3.5 CD or so. Taking each of the red, green, and blue LEDs to form a lighting unit would have a total luminosity of about 15 CD. However, taking three white LEDs to form a light unit would have a total luminosity between 6 to 8 CD. Considering the price, the three red, green, and blue LEDs would cost about ⅔ of the price of three white LEDs. Therefore, the luminaire composed of the RGB LEDs for now and the near future definitely would be more practical than using white LEDs. It can also achieve the effect of varying color by controlling the output of each single color LED.
Since the beam shape
11
(as shown in
FIG. 2
) of the red LED
1
(as shown in
FIG. 1
) is different from those beam shapes
21
,
31
(shown in
FIG. 4
) of the blue LED
2
and the green LED
3
(shown in FIG.
3
), respectively, therefore, when all three colors are projected on an object it will not be perfectly white and has inhomogeneous speckles
101
on the rim of the beam. The reason is that the red LED
1
only need one whisker, thus the central area is dark and the light beam after a resin lens has a circular shape (as shown in FIG.
2
). The blue and green LEDs
2
,
3
need two whiskers for electric conduction, these two whiskers usually set on the diagonals. Thus the dark areas of the chip rest on the diagonals. After the projection through lenses, the beams become elliptical (as shown in FIG.
4
). This shape is not easy to be modified by a correction resin lens because mass production could not assume the precision required. Accordingly, when those two LEDs
2
,
3
and the red LED
1
combine to form a luminaire, beams of different colors would have different projection shapes (shown in
FIG. 5
) and red speckles
101
form at places where blue and green light cannot reach.
There are various methods for solving the above situation. One is to place lenses with different refractivities in front of the LEDs so that the lenses can have different refractive effects on lights from individual LEDs. This method, however, is not practical. Not only does the lens cost too much, the lens also has to be redesigned once the arrangement of the LEDs changes. Another method is to place a dispersion plate in front of the LEDs to fully mix all colors and the light emerging therefrom would be very homogeneous. Yet the application of the luminaire would be limited because the dispersed light can not be focused and has a lower luminosity.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a light-emitting diode (LED) light source and, more particularly, a structure of lighting units that homogeneously mix the light beams from LEDs of different shapes to achieve a superior light mixing effect.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
REFERENCES:
patent: 5276380 (1994-01-01), Tang
patent: 5641611 (1997-06-01), Shieh et al.
patent: 403171780 (1991-07-01), None
patent: 406076049 (1994-03-01), None
News VCSEL—Technical Information Support—Published by TrueLight Corporation.
O'Shea Sandra
Sawhney Hargobind S.
Troxell Law Office PLLC
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